A tale of 2 sandbars: A Florida coastline somewhat unusual

Monday

Where do they come from? What lives on and between them? How do they affect swimming?

PANAMA CITY BEACH — Just offshore, a kind of river runs parallel to the coastline of Panama City Beach.

Despite having no name, it’s one of the places most frequented by tourists, who often stand on its two ever changing banks — the first and the second sandbars.

The two sandbars — and the trough that flows between them — are one of the most distinctive features of PCB’s coastline, hosting a diverse ecosystem and and controlling how water rushes away from the shoreline.

They can be a peaceful rest for swimmers, or the force behind a rip current. They can be a protective shelter for baitfish, or they can be a hunting tool for sharks.

Either way, they form one of the most distinctive features of the beach.

Where do they come from?

Double sandbar systems aren’t uncommon, but they also aren’t found everywhere, according to a handful of coastal engineers and scientists interviewed.

Some beaches, like Panama City Beach and Fire Island N.Y., have them permanently. In other cases, such as on the Atlantic Coast of Florida, they might pop up for a season and then gradually level out.

It all depends on the waves.

Coastal engineer Stephen Keehn with APTMI coastal engineering, a company with which the Bay Tourist Development Council contracts, explained how the wave climate in Panama City Beach — a combination of big and small waves — creates the two sandbars.

The smaller waves, he said, form the nearshore sandbar, which at times can attach to the coastline, as happened in places after Subtropical Storm Alberto blew through last month. The larger waves tend to control the second, and more stable, sandbar a bit farther offshore.

The slope of the Gulf’s floor also might factor in, Keehn said, noting PCB “has some pretty deep water offshore that ... may factor into the two-bar presence.”

Charlie Paxton, a certified consulting meteorologist whose Ph.D. research focused on sandbars and riptides, said areas with “relatively gentle waves” like the Gulf are more likely to form two sandbars.

The bottom line and easiest way to think about it, according to Lisa Armbruster the beach consultant for the TDC, is that the two sandbars are “consistent, natural features of our beaches that are a result of wave and current action depositing sand.”

What lives there?

The trough between the sandbars makes for ideal habitat for aquatic life looking for a break from the pounding of the surf.

“Fish tend to aggregate there because is a little protection,” said George Burgess, the former director of the shark program at the University of Florida.

The channel, he said, can be thought of as an underwater river, with its own unique habitat and properties.

“It’s actually a pretty diverse community,” said Eric Sander, a biologist with the Florida Fish and Wildlife Conservation Commission. “You don’t see much, but it’s there.”

There are the tiny creatures, like the blue crabs, lady crabs and calico crabs that scuttle around the bottom. There are the baitfish, particularly species in the herring school, that like to hide from the waves in the trough and the added shelter the space provides from predators. There are the moderately sized fish, like the mangrove snapper. And then, there are the bigger more predatory fish, drawn in by the ample supply of bait.

“What’s unique is very large, offshore fish will be caught right offshore,” Sander said. On the East Coast, he said, “you don’t see sailfish until you are considerable distance offshore,” but that’s not the case for anglers on the PCB piers, where sailfish are caught on occasion.

Sanders believes it’s an offshore current that brings the fish closer in, coupled with number of baitfish in the trough.

“The food is what holds then there,” he said.

It’s also what brings the apex predator to the trough — the sharks.

“It’s a highway for the sharks,” Burgess said.

Sharks will hunt anywhere the water is deep enough to swim, but the space between the sandbars is a common spot for them because the hunting is so good. The four species most likely to spotted between the sandbars are blacktip, spinner, blacknose and sharpnose sharks, Burgess said. However, sharks from the hammerhead family — including bonnetheads, scalloped hammerheads and great hammerheads — as well as finetooth and lemon sharks can all be found there, Sanders said.

And occasionally, a bull shark, one of the most aggressive species, is spotted cruising the highway, looking for a meal.

While the sharks are frequent visitors, it is worth noting it is rare for them to interact with people. Since 1900, only eight shark bites have been recorded in Panama City Beach. The two attacks that were fatal happened offshore, in snorkeling and free diving incidents.

It’s also worth noting the troughs don’t create massive schools of sharks, but rather are a gathering point — kind of like the line at a fast food place, Burgess said — for sharks.

“There are all solitary species, but they will aggregate around a common resource,” Burgess said. “You might find a number of sharks in one trough, but you might not.”

How does this affect swimmers?

Master swimmer, former lifeguard and Panama City Beach Councilman Paul Casto likes to swim between the sandbars on calm days.

“It’s deep, it’s a little closer to the shore, and there’s less traffic,” he said, though on choppy days, “it turns into a washing machine.”

The trough can be a gentle swim, but the sandbars around it can also shift to create the rip currents — channeled rushes of water pulling away from shore — that have caused so many drownings and near drownings over the years.

“There was a time I got caught in one when I was a teenager. I just moved down here, and I didn’t know what it was,” Casto said. “The hard part is not panicking.”

With the waves changing the sandbars all the time, the currents change, too, said Tabitha Kimball, the Bay County Beach Operations supervisor. Rip currents, she said, can happen anywhere.

“You are always going to have rip currents,” she said. “You are always going to have sandbars.”

Rip currents often form near structures in the water such as piers or jetties, when wave heights change suddenly, or most frequently when a channel is cut into a sandbar, creating a path for water from waves to return to the depths. The water can move as quickly as eight feet per second, faster than an Olympic swimmer.

So far, there are no studies proving double sandbar systems spell double trouble, said Paxton and Mark Wool, the warning coordinator for the National Weather Service of Tallahassee. Two sandbars do not mean more rip currents will be created, nor does it definitively mean the current will be more powerful if it cuts through both.

However, Casto said in his experience, swimming the channel is “absolutely” is more powerful if a current cuts through both. Wool said that would, “in a qualitative sense,” be logical.

If people are caught in current, instead of trying to swim directly to shore — which is like trying to swim upstream in a fast moving river — swim to the side until out of the water’s pull. Once out of the rip current’s channel, it should be easier to swim back to shore.

Not panicking and wasting energy, experts warned, is key.

The currents can be spotted from shore based on how the water is moving, but for people who aren’t experts, Kimball said to swim near a lifeguard and not be afraid to ask the lifeguards where the currents are. The county also has started putting out sandwich boards indicating where rip currents are.

“The lifeguards love to educate,” Kimball added. “They’d rather do that than have to potential save your life, though they will do that as well.”

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